This article was previously published under Q286717
After you install Windows XP on an IBM ThinkPad portable computer (model A20M, A21M, or X20), Device Manager displays the following error message, which is marked with a yellow icon:
UNKNOWN DEVICE Code 28 -- No drivers are installed for this device. The location of the device is listed on LOCATION: on Microsoft ACPI-Compliant Embedded Controller.
This behavior occurs because Windows XP has no built-in Advanced Configuration and Power Interface (ACPI) driver for the embedded ACPI controller that comes with these models of the IBM ThinkPad portable computer.
To resolve this behavior, contact IBM to obtain an updated driver for the embedded ACPI controller.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.
For more information about hardware and software vendor contact information, visit the following Microsoft Web site: